The present invention relates to an improvement of a sliding member for a window regulator, and more particularly to an improvement of a sliding member capable of minimizing an instability of a sliding member relative to a guide rail.
With regard to a conventional window regulator which moves up and down a window pane for vehicles or the like by sliding to open or shut the window, there is employed for example a regulator having a construction in which a steel guide rail having a "lip channel steel" cross sectional shape (both sides are twice bent inwardly) is used and a sliding member capable of sliding along the inside of the guide rail is attached to a carrier plate.
The bending of the guide rail having the above-mentioned cross sectional shape is easy compared with guide rails having different cross sectional shape, so the guide rail having the above-mentioned cross sectional shape is widely used for a window regulator which needs to make a window pane slide along a three dimensional locus. In order that the carrier plate to which a window pane is attached can slide along the guide rail having the above-mentioned construction, the carrier plate is equipped with a pivotally attached sliding member made of metal or relatively hard synthetic resin to allow the guide plate to slide along the guide rail.
With regard to the conventional sliding member for a window regulator, metal or relatively hard thermoplastic resin (polyacetal or the like) is generally employed as the material to be used for the member. On the other hand, in another example of the conventional window regulator, a comparatively hard but elastic material, such as polyurethane, is used and its elasticity is effectively utilized.
The former sliding member is hardly bent even when a heavy load is applied onto it during sliding movement in the guide rail, so it can stand under a heavy load. However, a clearance to ensure a smooth initial sliding movement is required between the sliding member and the guide rail, though the required clearance is very small. This clearance causes a pivotal instability of the carrier plate supporting the window pane during its sliding movement, and thus there arises an inconvenience problem in the opening and shutting operation of the window pane.
On the other hand, the latter sliding member made of elastic polyurethane or the like does not cause a play initially in the sliding movement, but it has a drawback that a deformation takes place and consequently a pivotal instability of the carrier plate takes place when a heavy load is applied onto it.
Thus, the former and the latter respectively have both a merit and a demerit.
In this specification, the term "pivotal instability" is defined as follows (refer to FIG. 7): ##EQU1##
An object of the present invention is to provide a sliding member capable of suppressing a pivotal instability at the initial sliding movement and another pivotal instability caused by undersired deformation under a heavy load to a minimum load.